Rocker chairs, including recliners with a rocking feature, typically have a base assembly for supporting the superstructure of the chair. For instance, FIG. 1 shows an exemplary multi-bar linkage system 10 of a rocker-recliner chair frame that controls the positioning of an overlying seat upon which a chair occupant sits. The linkage system 10 allows a person to apply backward pressure while seated to move the frame of the chair into a reclined position and downward pressure on a foot support of the frame to return the chair frame to the upright seated position. A lower portion 12 of the linkage system 10 is connected to a rocker chair base assembly 20 that allows the chair occupant to rock back and forth in a forward and backward motion similar to a standard rocking chair.
A left side portion of a conventional rocker chair base assembly 20 is shown in FIG. 1, with the right side generally being a mirror image of the left side. The rocker chair base assembly 20 includes a pair of cam assemblies 30, one on the left side portion of the assembly 20 and one on the right side portion of the assembly 20. The cam assemblies 30 provide the interface between the linkage system 10 and a set of spaced apart left side and right side longitudinal rails 40 that support the chair on a floor. Additionally, the base assembly 20 includes a set of cross tubes 50 interconnecting the cam assemblies 30 and a pair of rocker spring assemblies 60 mounted with the cross tubes 50 for regulating the degree of forward and backward rocking motion of the cam assemblies 30 on the longitudinal rails 40. Each cam assembly 30 is formed by an L-shaped upper bracket 32 welded to the longitudinal ends of an upper pair 52 of the cross tubes 50 and a lower wooden cam member 34 attached to the upper bracket 32, with the upper bracket 32 welded or otherwise secured with linkage system lower portion 12. The cam member 34 has a generally arcuate contact surface for rolling engagement with an upper flat surface of the respective longitudinal rail 40.
Despite the widespread use of the aforementioned cam assemblies 30, the conventional design has a number of drawbacks. First, the contact surface of a wooden cam member 34 tends to distort over repeated load cycles, leading to a flattening of the arcuate shape and an inconsistent rocking pattern. This flattening effect may be exacerbated by hardness variations present in a section of wood selected to form the cam member 34. Another problem with the conventional cam assembly design is installation on a rocker chair base assembly 20. The metal upper bracket 32 is usually welded to the cross tubes 52, which is time consuming and labor intensive, and may result in imprecise lateral positioning of the cam assemblies 30 on the longitudinal rails 40. Further, attaching the upper bracket 32 and cam member 34 together with fasteners may result in weakening of the wood near the point of attachment, shortening the life of the cam assembly 30. Some of the problems associated with using fasteners can be avoided by the use of adhesives to secure the upper bracket 32 with a top surface of the cam member 34. However, adhesives are themselves often subject to failure over time. Additionally, even with adhesives, precise assembly steps are still required to avoid misalignment of the cam member 34 relative to the longitudinal rails 40. As can be seen, fabrication of a conventional rocker chair base assembly 20 incorporating the aforementioned cam assembly 30 design is a labor intensive and time consuming process.